Im not sure how it works really but I wouldnt use it incase maybe some of washingliquid stuff could have got in to it - this may be impossible I am not sure - but if is possibly then you wouldnt want to inhale that during an attack
I've done this before... But I had a spare so didn't try it. I reckon it'll be fine to use if necessary (you can but try). I'd order a new prescription as soon as I could though. It's always good to have a spare. I have at least 4 in various places.